Tube base and socket



Feh 18, W36. A, HOROWITZ ET AL 2,?03L

TUBE BASE AND SOCKET Filed Feb. 26, 1935 Patented Feb. 18, 1936 PATENT OFFICE TUBE BASE AND SOCKET Alexandre Horowitz and Jean Visman, Eindhoven, Netherlands, assignors to' Radio Corporation of America, a corporation of Delaware Application February 26, 1935, Serial No. 8,298 In Austria March 1, 1934 4 Claims.

The invention relates to bases and sockets for electron discharge tubes, and more particularly to bases and sockets in which a large number of contacts are arranged in a desirable manner.

Oneobject of the invention is to provide a thermionic tube base with improved construction and arrangement of contact pins.

" A furtherobject of the invention is to provide an improved socket adapted for use with the new tube base.

To increase the number of contacts on the usual type of base it appears to be necessary to increase the length and diameter of the base. With the present bases it seems impractical to attempt to accommodate the tube in a socket in such manner that the tube with its socket does not require more lateral space than the tube itself,- u nless the diameter of. the base is substantially reduced at the seal with respect to the diameter of the tube. For this reason, as well as to reduce the overall length of the tube, base, and socket, the connection by means of the usual axial plug pins has to be renounced because either the pins or the socket contacts receiving them considerably increase the necessary distance between the end of the tube and the contact connection of the leads with the socket. The conflict between the suitable accommodation of a great many contacts and said requirements is due to the fact that the absolute values of the distances between the contacts are dictated by a minimum length of path for the surface leakage currents between contacts and by the capacity efiects between contacts and leads. Theincrease of the number of contacts consequently gives rise to an increase in the size of the base circle of. the cylindrical base which therefore must become larger than the known bases and consequently also larger than the diameter of the glass bulb at the seal.

A specific object of the invention, therefore, is to provide a form of construction whereby the diameter of the base may be made less than the diameter of the bulb at the seal. For this purpose the contacts are divided into two groups of approximately equal numbers. This division may be made in accordance with the division of electrodes of a tube which may be divided into two groups. That is, the electrodes comprise those to which a fixed potential and those to which an alternating potential may be applied. Quite distinct portions of the circumference of the circle are'allotted to said two groups in such manner that to one group of contacts is given a portion of the circumference which is about three times as large as that allotted to the other group. The resulting difference in spacing is rendered feasible by the fact that with the different groups of contacts which are allotted to the above mentioned different groups of electrodes, the requirement of maintaining determined spacmg is based on different considerations. The value of the inter-contact capacity is controlling in determining the spacing of those contacts which are connected to electrodes having an alternating current potential. The requirement of maintaining a determined spacing between D. C. contacts is based on the necessity of keeping the resistance to surface leakage currents above a determined minimum value. I

According to the invention, the last mentioned group of contacts, in which the distances are essentially determined by the resistance to surface leakage currents, are concentrated on a sector of. a circle the entire angle of which is approximately or smaller than 90. If the leakage paths between the contacts thus grouped together would have no longer the required length, they are given, if desired, with the aid of artificial ,means (such as ribs, holes, slits and the like) the required minimum length. Owing to the concentration of one of the groups on about one-quarter of the circumference of the circle the distances between the contacts of the other group become large enough to arrange the contacts with suitable distances on the arc of 270 even in the case of a reduced diameter.

In order to obtain the smallest possible diameter of the base, the contacts are arranged radially so as to protrude from the outer surface of. the cylindrical base. They are, further, given the shape of wedges so that in spite of the radial arrangement of the contacts the surfaces of adjacent contacts have at all points approximately the same distance. This ensures an increased width of the protruding heads of the contacts while at all points of the surfaces, even in the group of the concentrated contacts, a constant spacing is maintained.

The invention will be more clearly understood by referring to the accompanying drawing in which Figure 1 represents a sectional view of the preferred form of our novel base construction; Figure 2 is a bottom view of the base shown in Figure 1'; Figure 3 shows a modified form of our tube base; Figure 4 is a bottom view of the base shown in Figure 3; and Figure 5 illustrates a novel socket arrangement adapted for use with our tube base. Like reference characters in the several figures represent similar parts.

Referring to Figures 1 and 2 of the drawing, the base for our tube comprises a cup-shaped member 2, preferably of insulating material which is formed of a cylindrical body with a closure means or bottom 1. Four contacts or lugs la, lb, lc, Id of the contacts or lugs I of the base are combined to form a group a which is concentrated on a sector of approximately 90 or less. As the distance between said contacts is extremely small, it may occur that there does not exist the minimum distance required with respect to leakage paths.

In this case the leakage paths are increased by artificial means 3, for example by means of radial ribs or slits. By this construction, it is obvious that the distance between contacts along the surface of the base is increased.

The second group b of contacts extends over a substantially greater proportion of the circumference of the base. By way of example, Figure 2 suggests 270, or three-quarters of the circle. Notwithstanding the small diameter of the base, the contacts of said group are spaced apart by a sufficient distance which is substantially not less than the distance between the contacts of the usual bases of larger diameter and fewer contacts. The group a of contacts is connected in this case to those electrodes of the tube which have a fixed potential, whereas the group b is connected to the electrodes having an alternating potential. The grouping of contacts. of group a and of group b is suggested with the assumption in mind that electrode circuits carrying only direct current are, generally speaking, of lower potential than currents in electrode circuits carrying radio frequencies. It is evident, therefore, that the relative greater spacing of contacts of group b provides for minimum surface leakage resulting from high potentials as well as minimizes capacity efiects resulting from high frequencies.

The contacts I have the shape of wedges and their frontheads II project to a considerable extent from the edge of the base. Notwithstanding the radial position of the contacts said wedge shape allows of the surfaces of closely adjacent contacts being approximately parallel. This is particularly advantageous in those cases in which between the contacts there is still exactly the required minimum distance. The described wedgeshaped arrangement permits reduction of the diameter of the base portion which is to be introduced into the holder, notwithstanding the increase of the number of contacts with the consequent risk of said contacts acting upon one another.

Figures 3 and 4 show a modified and simplified form of our invention in which the radial grooves between contacts I have been omitted. Such construction is permissible where the leakage path between contacts is found to be sufficiently long.

The connections of the bases of electron discharge tubes to the supply and socket contacts is usually effected by means of contact pins to which the wires emerging from the tube are connected and which are pressed into corresponding contacts of a socket. However, the extension of the contact pins in the direction of the axis of the tube objectionably increases the length of the tube from the bottom end of the glass bulb of the tube to the connections of the socket contacts, a length which is sought to be reduced as much as possible since a minimum length is very important for a compact construction of the apparatus.

For this purpose it has been proposed above to secure current-carrying contacts for the base to the periphery of the cylindrical tube base. In this case the socket is provided with springs which are pressed down by the contacts of the periphery of the base when the base is inserted in the socket.

Where the usual axial pins are omitted, certain objectionable features in manufacture arise. The manufacture is comparatively complicated since it is difiicult to connect the wires emerging from the tube to the contacts provided at the periphery. As the base is closed by a bottom, it is dinicult to securely connect said wires to the periphery contacts.

Accordingly, a further object of the invention is to provide a base of the type referred to in which, however, the said drawbacks are entirely avoided. For this purpose the wedge-shaped contacts I that bear on the springs III of the socket are provided with extensions 4, projecting inwardly into the cylindrical hollow space of the cap. These extensions are provided with holes 6 bored in the axial direction of the tube through which holes the wires emerging from the bulb can be slipped. The inner end of said extension is rolled or riveted to suitably secure the contact to the base. A longitudinal groove 5 is provided in each contact in which groove the end of the wire slipped through the hole may be laid for soldering.

A base and contact of this type substantially simplifies the manufacture of the tube. The ends of the connecting wires emerging from the press and stem of the tube are positioned by means of a gauge so that when inserted in the base in an axial direction they register with the axial holes 6 in the contacts and traverse the radial grooves 5 of the contacts. In this case their ends may be bent and forced into the grooves. The. bending of the wires into the grooves and the attachment of the wire ends to the contacts may then be effected by dip-soldering; that is, by simply immersing the contacts in molten solder. Besides simplifying manufacture, this construction provides a large, oblong area of contact between the connecting or lead-in wires and the contact members I. This connection results in good electrical contact as well as high mechanical strength.

For the purpose of providing good electrical contacts between lugs or contacts and the contacts of the socket, longitudinal springs In, Figure 5, are used in such a manner that the bottom end of leg l2 thereof is movably mounted. It is apparent that with this arrangement, the tube base is resiliently retained after its insertion in the socket. A particularly firm engagement of base and socket is insured because of the oblique position of leg I2 of the springs In with respect to the contact members I, resulting in a downwardly directed component of force on the contacts. Spring l0 comprises a second leg H which is secured to the inner wall of the socket by means of a stamped out shoulder or hook portion I 6.

Many other modifications of the invention will suggest themselves to those skilled in the art, and it is desired that the scope of the invention shall not be limited except by the prior art and as defined in the appended claims.

What we claim as new is:

1. In a base for thermionic discharge devices; a hollow cylindrical shaped body of insulating material; closure means for one end of said body; and aplurality of fiatwedge-shaped contactmembers secured with one side of each member to the outer surface of said closure means and with the.

broad ends of said contact members arranged to protrude radially beyond the periphery of said closure means, the edges of said members converging toward the center of said closure means, the edges of adjacent members being substantial- 1y parallel.

2. In a base for tubes; a hollow cylindrical shaped body of insulating material; closure means for one end of said body; elongated contact members secured to the outer surface of said closure means, the securing means comprising a hollow lug portion of said contact members extending through said closure means, said contact members being arranged to protrude radially outward from the edge of said closure means, and means for electrically and mechanically connecting said members to lead wires through the opening in said lug comprising grooves in said members intersecting the outer ends of the lug openings.

3. In a base for tubes; a hollow cup-shaped body of insulating material; a bottom portion for said body; elongated flat wedge-shaped contact members secured to the outer surface of said bottom portion, the large end of said contact members being arranged to protrude outwardly from the edge of said bottom portion and beyond the periphery of said body and the edges of adjacent contact members being substantially parallel and arranged to converge toward the center of said bottom portion.

4. In a base for tubes; a hollow cylinder; closure means for one end of said cylinder; contact members with their sides secured to the outer surface of said closure means and arranged to protrude beyond the edge of said closure means; a groove in an outer surface of said contact means and an opening through said contact means in registry with said groove.

ALEXANDRE HOROWITZ. JEAN VISMAN. 

